Kevin Clifford / AP Photo

Mary Kaye Huntsman, the wife of GOP presidential candidate Jon Hunstman, responded Saturday to an attack ad released by a group called “NHLiberty4Paul,” tagging the former Chinese ambassador as “the Manchurian Candidate” and showing a video of him with his young daughter Gracie Mae, one of two daughters the Huntsmans adopted from desperate circumstances in Asia and have raised from infancy.

“I can’t even watch it because my daughters are the world to us,” Mrs. Huntsman said in an interview with The Daily Beast at the Main Street Station Diner in the tiny town of Plymouth. “My concern, my first thought was, what is Gracie going to think when she sees this?”

Gracie, now 12, was found abandoned in a vegetable market in China, while her sister, Asha, 6, was left in a field in India on the day she was born. The Huntsmans have five other children, in addition to Gracie and Asha.

“Whoever did it is absolutely disgusting, and there is no place for anything like that. We would never do anything like that,” she said. “Jon will always be fair. He may contrast where he is and where another candidate is, but he will never stoop low and go to the core of somebody’s character.”

The ad is reminiscent of one of the darkest episodes in the 2000 election, when mailers targeting John McCain in South Carolina intimated that McCain had an interracial child outside of his marriage, when in fact the child was his young daughter, Bridget, whom Cindy McCain adopted during a humanitarian mission to Bangladesh.

It’s the sort of deeply personal, anonymous attack that families in politics fear the most, but the Hunstmans were smiling Saturday and focused on getting voters out to the polls for Tuesday’s primary, the contest that is now a make-or-break event for his campaign after he chose to forgo the Iowa caucuses last week.

As Jon Hunstman works the breakfast crowd in the cramped diner on Main Street, Mary Kaye Hunstman reaches out with a smile to anyone he may have missed, and follows up with people he chatted up earlier to offer an extra insight or answer one more question.

“I try to get out and let people know what his heart and soul are,” she told me as what she sees as her role in the campaign. “He doesn’t pander, he’s genuine, he’s honest, and he’s sincere.”

But she’s also ready to list the specific attributes she sees as making him the best man for the job of president in 2012.

“When you’re looking for what you’re going to vote for, there are four things-- government service, business experience, extensive foreign policy, and someone who can unite the country,” she said. “He has the ability to bring Republicans, independents, and some Democrats together and that’s something this country needs.”

After months of days and nights of shaking hands, doing interviews, speaking out on her husband’s behalf, and the controversy over the Paul supporters’ ad, Mary Kaye Huntsman says she’s getting through to Tuesday on one thing: “I think adrenaline, no sleep. It’s like a marathon and you know that to get to Tuesday, you just have to keep focused.”

Above and beyond the debate prep and briefing books and events at diners and bookstores, Mary Kaye Huntsman said she mostly wants to help her husband and family get through the gauntlet of the presidential campaign.